The principal objective of this study is to elucidate metabolic and biological functions of polyunsaturated fatty acids, docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6) in the nervous system with particular reference to their modulation by ethanol. We have previously found that 22:6n-3 promotes the accumulation of phosphatidylserine (PS), which is thought to be involved in growth factor signaling leading to cell survival. During this period, the effect of polyunsaturates on the survival of neuronal cells was further investigated along with the underlying mechanisms of this effect. The results obtained by the differential sedimentation assay, DNA ladder formation and Hoechst staining as well as caspase-3 activity assay consistently indicated that 22:6n-3 prevented the apoptotic cell death of both Neuro 2A and PC-12 cells, but only after a prolonged period of enrichment. Phospholipid molecular species analysis by electrospray LC/MS revealed that the extent of protective effect correlated with the incorporation of 22:6n-3 into PS, suggesting that 22:6n-3 as a membrane phospholipid constituent, especially as PS, may be important for the protective effect. According to in vitro biomolecular interaction analysis, the interaction between unilamellar vesicles of phospholipids and Raf-1 kinase required the presence of PS in the vesicle and the extent of interaction was indeed dependent on the PS composition. These results appear to support the view that PS accumulation promoted by 22:6n-3 may be important in growth factor signaling. We also found during this period that melatonin, the major product of the pineal gland, regulates polyunsaturated fatty acid metabolism at both PLA2 and 12-lipoxygenase levels, suggesting a role of polyunsaturated fatty acids in biochemical functions involving melatonin. - docosahexaenoic acid, apoptosis, Neuronal cells, phosphatidylserine, melatonin, ethanol, PLA2, lipoxygenase, pineal, mass spectrometry